1. Field of the Invention
Embodiments of the invention generally relate to safety valves disposed concentrically within a tubular. More particularly, embodiments of the invention relate to a subsurface safety valve having a seal assembly to seal an annulus between the outside of the valve and the tubular.
2. Description of the Related Art
Surface-controlled, subsurface safety valves (SCSSVs) are commonly used to shut-in oil and gas wells. The SCSSV fits into a production tubing in a hydrocarbon producing well and operates to block the flow of formation fluid upwardly through the production tubing should a failure or hazardous condition occur at the well surface. The production tubing may include a ported landing nipple designed to receive the SCSSV therein such that the SCSSV may be installed and retrieved by wireline. During conventional methods for run-in of the SCSSV to the landing nipple, a tool used to lock the SCSSV in place within the nipple also temporarily holds the SCSSV open until the SCSSV is locked in place.
Most SCSSVs are “normally closed” valves, i.e., the valves utilize a flapper type closure mechanism biased to a closed position. During normal production, application of hydraulic fluid pressure transmitted to an actuator of the SCSSV maintains the SCSSV in an open position. A control line that resides within the annulus between the production tubing and a well casing may supply the hydraulic pressure to a port in the nipple that permits fluid communication with the actuator of the SCSSV. In many commercially available SCSSVs, the actuator used to overcome the bias to the closed position is a hydraulic actuator that may include a rod piston or concentric annular piston. During well production, the flapper is maintained in the open position by a flow tube acted on by the piston to selectively open the flapper member in the SCSSV. Any loss of hydraulic pressure in the control line causes the piston and actuated flow tube to retract, which causes the SCSSV to return to the normally closed position. Thus, the SCSSV provides a shutoff of production flow once the hydraulic pressure in the control line is released. The bias to the normally closed position may be caused by a powerful spring and/or gas charge that biases the actuator and a torsion spring and a response to upwardly flowing formation fluid that causes the flapper to rotate about a hinge pin to the closed position.
The landing nipple within the production tubing may become damaged by operations that occur through the nipple prior to setting the SCSSV in the landing nipple. For example, operations such as snubbing and tool running using coiled tubing and slick line can form gouges, grooves, and/or ridges along the inside surface of the nipple as the operations pass through the nipple. Further, any debris on the inside surface of the nipple or any out of roundness of the nipple may prevent proper sealing of the SCSSV within the nipple. Failure of the SCSSV to seal in the nipple due to surface irregularities in the inner diameter of the nipple can prevent proper operation of the actuator to open the SCSSV and can prevent the SCSSV from completely shutting-in the well when the SCSSV is closed since fluid can pass through the annular area between the SCSSV and the nipple due to the irregularities. Operating the well without a safety valve or with a safety valve that does not function properly presents a significant danger. Thus, the current solution to conserve the safety in wells having damaged nipples includes an expensive and time consuming work over to replace the damaged nipples.
Therefore, a need exists for an apparatus and method for disposing an SCSSV within a tubular having a damaged or irregular inside surface. There exists a further need for an SCSSV that can be set and sealed within a damaged landing nipple using conventional methods. Further, a need exists for an SCSSV that provides a large inner diameter flow path while sealing an annulus between the outside of the SCSSV and an irregular inner surface of a landing nipple.